1. Technical Field
The disclosure concerns a remote plasma source for use in a plasma processing system.
2. Background Discussion
Etching applications increasingly require precise control of ions and radical species to treat (e.g., etch) the workpiece with high selectivity in a main process chamber. The workpiece may be a semiconductor wafer, for example. One method to achieve this is to use a remote plasma source with the main process chamber, which provides desired species to interact with the workpiece in the main chamber. A high density plasma is desired to achieve high etch rates on the workpiece. Therefore, high pressure operation is preferred, which increases gas density and plasma density. Inductively coupled plasma sources in the remote plasma source are not preferred due to the difficulty of igniting a plasma in this pressure range. A capacitively coupled plasma source (driven with an RF or DC voltage) is therefore preferred in the remote plasma source. A disadvantage of this approach is that the ions produced in a capacitively coupled remote plasma source have high energy and can bombard the remote plasma source surfaces, generating particle and/or metal contaminants which are drawn into the main chamber and land on the workpiece, impairing productivity. What is needed is a way of generating a high density plasma in the remote plasma source while minimizing ion sputtering of the remote plasma source hardware.